let arr = [1,2,3,4];
// 1. for arr2
// let arr2 = arr 浅拷贝 引用式赋值
let arr2 = arr.slice(0);
arr2[1] = 6;
console.log(arr,arr2)
var arr3 = [{name:"weifeng"},{"name":"boy"}]
var arr4 = [].concat(arr)
arr4[1].name = "lilis"
console.log(arr4,arr3)

